Euro Zone's Smaller Banks Required to Set Aside Only 7% of Assets

FRANKFURT—The European Central Bank will force the euro zone's largest banks to set aside 8% of their risk-adjusted assets as a capital buffer, which will form one plank of the ECB's assessment of bank balance sheets next year, according to a person familiar with the matter.

Euro-zone banks, which will be supervised by the ECB starting at the end of next year, will be required to hold a 7% capital buffer. The region's most...